The pathophysiology of cerebral ischemia involves multiple mechanisms including neuroinflammation mediated by activated microglia and infiltrating macrophages/monocytes. The present study employed a rat permanent middle cerebral artery occlusion (pMCAO) model to study effects of histone deacetylase (HDAC) inhibition on ischemia-induced brain infarction, neuroinflammation, gene expression, and neurological deficits. We found that post-pMCAO injections with HDAC inhibitors, valproic acid (VPA), sodium butyrate (SB), or trichostatin A (TSA), decreased brain infarct volume. Postinsult treatment with VPA or SB also suppressed microglial activation, reduced the number of microglia, and inhibited other inflammatory markers in the ischemic brain. The reduction in levels of acetylated histone H3 in the ischemic brain was prevented by treatment with VPA, SB, or TSA. Moreover, injections with HDAC inhibitors superinduced heat-shock protein 70 and blocked pMCAO-induced down-regulation of phospho-Akt, as well as ischemia-elicited up-regulation of p53, inducible nitric oxide synthase, and cyclooxygenase-2. The motor, sensory, and reflex performance of pMCAO rats was improved by VPA, SB, or TSA treatment. The beneficial effects of SB and VPA in reducing brain infarct volume and neurological deficits occurred when either drug was administrated at least 3 h after ischemic onset, and the behavioral improvement was long-lasting. Together, our results demonstrate robust neuroprotective effects of HDAC inhibitors against cerebral ischemia-induced brain injury. The neuroprotection probably involves multiple mechanisms including suppression of ischemia-induced cerebral inflammation. Given that there is no effective treatment for stroke, HDAC inhibitors, such as VPA, SB, and TSA, should be evaluated for their potential use for clinical trials in stroke patients.Stroke, also referred to as cerebral ischemia, is a pathological condition resulting from occlusion or hemorrhage of blood vessels supplying oxygen and essential nutrients to the brain. In all cases, stroke ultimately induces death and/or dysfunction of brain cells, as well as neurological impairments that reflect the location and size of the ischemic brain area. Mechanisms leading to cell death during cerebral ischemic injury are complex, including excitotoxicity, ionic imbalance, oxidative/nitrosative stress, and inflammation (for review, see Lo et al., 2003). It is increasingly recognized that cerebral inflammation mediated by activated microglia and infiltrating leukocytes, including monocytes/macrophages, also plays a key role in focal ischemia-induced neurodegeneration. Activated microglia and invading leukocytes exert a cytotoxic function by releasing proinflammatory cytokine factors (IL-1, IL-2, and TNF-␣), nitric oxide (NO), and reactive oxygen species, which contribute to brain infarction and excitotoxicity (Gregersen et al., 2000).Valproic acid (2-propylpentanoic acid sodium salt; VPA), a drug commonly used to treat seizures and bipolar mood disorder, has been...

Valproate (VPA), one of the mood stabilizers and antiepileptic drugs, was recently found to inhibit histone deacetylases (HDAC). Increasing reports demonstrate that VPA has neurotrophic effects in diverse cell types including midbrain dopaminergic (DA) neurons. However, the origin and nature of the mediator of the neurotrophic effects are unclear. We have previously demonstrated that VPA prolongs the survival of midbrain DA neurons in lipopolysaccharide (LPS)-treated neuron-glia cultures through the inhibition of the release of pro-inflammatory factors from microglia. In this study, we report that VPA upregulates the expression of neurotrophic factors, including glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) from astrocytes and these effects may play a major role in mediating VPA-induced neurotrophic effects on DA neurons. Moreover, VPA pretreatment protects midbrain DA neurons from LPS or 1-methyl-4-phenylpyridinium (MPP þ )-induced neurotoxicity. Our study identifies astrocyte as a novel target for VPA to induce neurotrophic and neuroprotective actions in rat midbrain and shows a potential new role of cellular interactions between DA neurons and astrocytes. The neurotrophic and neuroprotective effects of VPA also suggest a utility of this drug for treating neurodegenerative disorders including Parkinson's disease. Moreover, the neurotrophic effects of VPA may contribute to the therapeutic action of this drug in treating bipolar mood disorder that involves a loss of neurons and glia in discrete brain areas.

Parkinson’s disease (PD) is characterized by the selective and progressive loss of dopaminergic (DA) neurons in the midbrain substantia nigra. Currently, available treatment is unable to alter PD progression. Previously, we demonstrated that valproic acid (VPA), a mood stabilizer, anticonvulsant and histone deacetylase (HDAC) inhibitor, increases the expression of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in astrocytes to protect DA neurons in midbrain neuron-glia cultures. The present study investigated whether these effects are due to HDAC inhibition and histone acetylation. Here, we show that two additional HDAC inhibitors, sodium butyrate (SB) and trichostatin A (TSA), mimic the survival-promoting and protective effects of VPA on DA neurons in neuron-glia cultures. Similar to VPA, both SB and TSA increased GDNF and BDNF transcripts in astrocytes in a time-dependent manner. Furthermore, marked increases in GDNF promoter activity and promoter-associated histone H3 acetylation were noted in astrocytes treated with all three compounds, where the time-course for acetylation was similar to that for gene transcription. Taken together, our results indicate that HDAC inhibitors up-regulate GDNF and BDNF expression in astrocytes and protect DA neurons, at least in part, through HDAC inhibition. This study indicates that astrocytes may be a critical neuroprotective mechanism of HDAC inhibitors, revealing a novel target for the treatment of psychiatric and neurodegenerative diseases.

Valproic acid (VPA), a widely prescribed drug for seizures and bipolar disorder, has been shown to be an inhibitor of histone deacetylase (HDAC). Our previous study has demonstrated that VPA pretreatment reduces lipopolysaccharide (LPS)-induced dopaminergic (DA) neurotoxicity through the inhibition of microglia over-activation. The aim of this study was to determine the mechanism underlying VPA-induced attenuation of microglia over-activation. Other HDAC inhibitors (HDACIs) were compared with VPA for their effects on microglial activity. We found that VPA induced apoptosis of microglia cells in a time and concentration-dependent manner. VPA-treated microglial cells showed typical apoptotic hallmarks including phosphatidylserine externalization, chromatin condensation and DNA fragmentation. Further studies revealed that trichostatin A (TSA) and sodium butyrate (SB), two structurally dissimilar HDACIs, also induced microglial apoptosis. The apoptosis of microglia was accompanied by the disruption of mitochondrial membrane potential and the enhancement of acetylation levels of the histone H3 protein. Moreover, pretreatment with Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access

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Summary The inflammatory effects of glycogen synthase kinase‐3 (GSK‐3) have been identified; however, the potential mechanism is still controversial. In this study, we investigated the effects of GSK‐3‐mediated interleukin‐10 (IL‐10) inhibition on lipopolysaccharide (LPS)‐induced inflammation. Treatment with GSK‐3 inhibitor significantly blocked LPS‐induced nitric oxide (NO) production as well as inducible NO synthase (iNOS) expression in BV2 murine microglial cells and primary rat microglia‐enriched cultures. Using an antibody array and enzyme‐linked immunosorbent assay, we found that GSK‐3‐inhibitor treatment blocked LPS‐induced upregulation of regulated on activation normal T‐cell expressed and secreted (RANTES) and increased IL‐10 expression. The time kinetics and dose–response relations were confirmed. Reverse transcription–polymerase chain reaction showed changes on the messenger RNA level as well. Inhibiting GSK‐3 using short‐interference RNA, and transfecting cells with dominant‐negative GSK‐3β, blocked LPS‐elicited NO and RANTES expression but increased IL‐10 expression. In contrast, GSK‐3β overexpression upregulated NO and RANTES but downregulated IL‐10 in LPS‐stimulated cells. Treating cells with anti‐IL‐10 neutralizing antibodies to prevent GSK‐3 from downregulating NO and RANTES showed that the anti‐inflammatory effects are, at least in part, IL‐10‐dependent. The involvement of Akt, extracellular signal‐regulated kinase, p38 mitogen‐activated protein kinase and nuclear factor‐κB that positively regulated IL‐10 was demonstrated. Furthermore, inhibiting GSK‐3 increased the nuclear translocation of transcription factors, that all important for IL‐10 expression, including CCAAT/enhancer‐binding protein beat (C/EBPβ), C/EBPδ, cAMP response binding element protein and NF‐κB. Taken together, these findings reveal that LPS induces iNOS/NO biosynthesis and RANTES production through a mechanism involving GSK‐3‐mediated IL‐10 downregulation.

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The amygdala is an important structure contributing to socio-emotional behavior. However, the role of the amygdala in autism remains inconclusive. In this study, we used the 28–35 days valproate (VPA)-induced rat model of autism to observe the autistic phenotypes and evaluate their synaptic characteristics in the lateral nucleus (LA) of the amygdala. The VPA-treated offspring demonstrated less social interaction, increased anxiety, enhanced fear learning and impaired fear memory extinction. Slice preparation and electrophysiological recordings of the amygdala showed significantly enhanced long-term potentiation (LTP) while stimulating the thalamic-amygdala pathway of the LA. In addition, the pair pulse facilitation (PPF) at 30- and 60-ms intervals decreased significantly. Whole-cell recordings of the LA pyramidal neurons showed an increased miniature excitatory postsynaptic current (EPSC) frequency and amplitude. The relative contributions of the AMPA receptor and NMDA receptor to the EPSCs did not differ significantly between groups. These results suggested that the enhancement of the presynaptic efficiency of excitatory synaptic transmission might be associated with hyperexcitibility and enhanced LTP in LA pyramidal neurons. Disruption of the synaptic excitatory/inhibitory (E/I) balance in the LA of VPA-treated rats might play certain roles in the development of behaviors in the rat that may be relevant to autism. Further experiments to demonstrate the direct link are warranted.